uneven fuel distribution

[Guest]

[tracer64]

  I pulled the plugs and cut them open, well, didnt really need to though to see the problem because it was pretty obvious.  I'm getting really uneven fuel distribution through the manifold (Vic Jr. )  My front plugs are all clean and look right, but as you go towards the back, especially #4 and #8, they are really rich at the top end, but also at an idle.  I'm currently running my 650 HP with the secondary PV blocked off with 72 primary jets and 80 secondary ones.  I'm gonna drop the secondarys down to 78's to see if that helps.  What do you guys  think?
  Oh, and the metering blocks in this doesnt have the removable IFR so I leaned the low speed AB's....not a good idea    Does anyone know of a place that sells metering blocks for the HP series with removable IFR's?

Thanks
Tracy
 

[86ssp]

Just curious about the pv block off.Why?You shouldn't need the block off.That may be the majority of the problem.I would put the correct pv in and check it.I go mid to high 9's with 2 pv's with good idle and part throttle.

[tracer64]

I was concerned witht he second PV wanting to open when driving around.    Is your secnd PV set lower than your primary one?

 
Tracy

[Heater]

Your 650 is jetted richer than my 750 


The last 650 I had was jetted (I think) 68's in the front and 73's in the rear with a block off on the rear and a 6.5 PV on the front.

[Thumper460]

The old HOLLEY rule was.. 4 jet sizes with the secondary P/V and a 10 spread without the P/V.  and then tune from there...

Tpr

[86ssp]

I was concerned witht he second PV wanting to open when driving around.    Is your secnd PV set lower than your primary one?essentially you are driving around with a pv that is open the second you start your motor.I gaurantee thats why your rear cylinders are richer than the front.I run a 2.5 pv on both sides because I have low vacuum with the cam I have.It all comes down to driveability.With out the pv you have to up the Jet to compensate.say you have 10 inwg at adle you would run a 5" pvThe only time that pv would open is when manifold vacuum drops below 5".At part throttle you will most likely have 12-15" at cruise,so theres no chance of the secondaries dumping all that fuel when its not needed.The only people I know that don't run a pv is for track only cars and they only want wot performance.I also know people that run Dominators on the street that still run a pv on both sides.A properly tuned carb will work on the street as well as the track.Putting the pv should help your rear cylinders lean out.What kind of fuel mileage do you get and what mileage do you want?I've seen 8 sec cars that have the driveability of most 13 sec. cars.It all comes down to your tuning capabilities.I can get 13-14mpg with my car with a big cam and alittle over 500hp at the crank.Before I learned all the circuits of the carb and how one circuit can effect another I was getting 3-5mpg and fouling plus after 200 miles.Now it runs as clean as an efi car.Do you have changeable hsab's and  iab's?

 
Tracy

[86ssp]

Let me know how much vacuum you have at idle.What are your cam specs?You shouldnt need to mess with the ifr's.If by chance you do,there is a trick to removing them with wet toilet paper.Then you drill and tap for the removable ones or you can press in blanks and start small and drill larger if needed.You really shouldn't have to go that far.

[tracer64]

How did you quote what I didnt say?

Yes, I have hsab and iab's (which I did try changing and that was bad )
My cam is 232/232 @ .050 with 108 lsa with .517 lift.  She idles with around 7" so I have a 3.5 in the front.
According to holley, this carb came from the factory with 70 jets square and front and rear pv.
I'll start back there.

Thanks

[86ssp]

I don't know what happened there ,it put my response in with your quote,wierd.Just a suggestion,put the carb back to the way it came out of the box and start over.jetting,hsab's,iab's,and so on.3.5 pv's is right for your vacuum.70-70pmj's would be a good place to start.You may end up with less jet than the 70-70.Good luck,Scott